Average Weather in San Fernando California, United States

In San Fernando, the summers are short, hot, arid, and clear and the winters are long, cool, wet, and partly cloudy. Over the course of the year, the temperature typically varies from 45°F to 92°F and is rarely below 38°F or above 100°F.

Based on the tourism score, the best time of year to visit San Fernando for warm-weather activities is from late May to mid October.

Temperature

The hot season lasts for 2.9 months, from June 24 to September 22, with an average daily high temperature above 86°F. The hottest day of the year is August 20, with an average high of 92°F and low of 65°F.

The cool season lasts for 3.8 months, from November 22 to March 14, with an average daily high temperature below 69°F. The coldest day of the year is December 25, with an average low of 45°F and high of 64°F.

The daily average high (red line) and low (blue line) temperature, with 25th to 75th and 10th to 90th percentile bands. The thin dotted lines are the corresponding average perceived temperatures.

The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Clouds

In San Fernando, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.

The clearer part of the year in San Fernando begins around April 25 and lasts for 6.3 months, ending around November 4. On September 7, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy91% of the time, and overcast or mostly cloudy9% of the time.

The cloudier part of the year begins around November 4 and lasts for 5.7 months, ending around April 25. On February 22, the cloudiest day of the year, the sky is overcast or mostly cloudy44% of the time, and clear, mostly clear, or partly cloudy56% of the time.

Precipitation

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in San Fernando varies throughout the year.

The wetter season lasts 4.1 months, from November 27 to March 30, with a greater than 11% chance of a given day being a wet day. The chance of a wet day peaks at 21% on February 20.

The drier season lasts 7.9 months, from March 30 to November 27. The smallest chance of a wet day is 0% on July 2.

Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 21% on February 20.

Daily Chance of Precipitation

The percentage of days in which various types of precipitation are observed, excluding trace quantities: rain alone, snow alone, and mixed (both rain and snow fell in the same day).

Rainfall

To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. San Fernando experiences significant seasonal variation in monthly rainfall.

The rainy period of the year lasts for 6.3 months, from October 16 to April 25, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around February 18, with an average total accumulation of 3.3 inches.

The rainless period of the year lasts for 5.7 months, from April 25 to October 16. The least rain falls around July 6, with an average total accumulation of 0.0 inches.

Average Monthly Rainfall

The average rainfall (solid line) accumulated over the course of a sliding 31-day period centered on the day in question, with 25th to 75th and 10th to 90th percentile bands. The thin dotted line is the corresponding average liquid-equivalent snowfall.

Sun

The length of the day in San Fernando varies significantly over the course of the year. In 2018, the shortest day is December 21, with 9 hours, 52 minutes of daylight; the longest day is June 21, with 14 hours, 27 minutes of daylight.

The number of hours during which the Sun is visible (black line). From bottom (most yellow) to top (most gray), the color bands indicate: full daylight, twilight (civil, nautical, and astronomical), and full night.

The earliest sunrise is at 5:41 AM on June 12, and the latest sunrise is 1 hour, 34 minutes later at 7:15 AM on November 3. The earliest sunset is at 4:43 PM on December 5, and the latest sunset is 3 hours, 26 minutes later at 8:09 PM on June 29.

Daylight saving time (DST) is observed in San Fernando during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.

The solar day over the course of the year 2018. From bottom to top, the black lines are the previous solar midnight, sunrise, solar noon, sunset, and the next solar midnight. The day, twilights (civil, nautical, and astronomical), and night are indicated by the color bands from yellow to gray. The transitions to and from daylight saving time are indicated by the 'DST' labels.

Humidity

We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.

The perceived humidity level in San Fernando, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, staying within 1% of 1% throughout.

Wind

This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.

The average hourly wind speed in San Fernando experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 6.0 months, from November 4 to May 5, with average wind speeds of more than 7.1 miles per hour. The windiest day of the year is December 31, with an average hourly wind speed of 9.0 miles per hour.

The calmer time of year lasts for 6.0 months, from May 5 to November 4. The calmest day of the year is August 14, with an average hourly wind speed of 5.3 miles per hour.

The average of mean hourly wind speeds (dark gray line), with 25th to 75th and 10th to 90th percentile bands.

The predominant average hourly wind direction in San Fernando varies throughout the year.

The wind is most often from the west for 3.4 months, from April 1 to July 12 and for 1.3 months, from August 24 to October 3, with a peak percentage of 50% on May 31. The wind is most often from the south for 1.4 months, from July 12 to August 24, with a peak percentage of 43% on July 30. The wind is most often from the north for 5.9 months, from October 3 to April 1, with a peak percentage of 50% on January 1.

Wind Direction

The percentage of hours in which the mean wind direction is from each of the four cardinal wind directions (north, east, south, and west), excluding hours in which the mean wind speed is less than 1 mph. The lightly tinted areas at the boundaries are the percentage of hours spent in the implied intermediate directions (northeast, southeast, southwest, and northwest).

Water Temperature

San Fernando is located near a large body of water (e.g., ocean, sea, or large lake). This section reports on the wide-area average surface temperature of that water.

The average water temperature experiences some seasonal variation over the course of the year.

The time of year with warmer water lasts for 3.3 months, from July 5 to October 14, with an average temperature above 66°F. The day of the year with the warmest water is August 22, with an average temperature of 68°F.

The time of year with cooler water lasts for 4.8 months, from December 11 to May 3, with an average temperature below 60°F. The day of the year with the coolest water is February 17, with an average temperature of 58°F.

The daily average water temperature (purple line), with 25th to 75th and 10th to 90th percentile bands.

Best Time of Year to Visit

To characterize how pleasant the weather is in San Fernando throughout the year, we compute two travel scores.

The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit San Fernando for general outdoor tourist activities is from late May to mid October, with a peak score in the first week of July.

The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit San Fernando for hot-weather activities is from early July to early September, with a peak score in the third week of August.

Methodology

For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.

Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.

Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.

Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.

Growing Season

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

Temperatures in San Fernando are sufficiently warm year round that it is not entirely meaningful to discuss the growing season in these terms. We nevertheless include the chart below as an illustration of the distribution of temperatures experienced throughout the year.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average growing degree days accumulated over the course of the year, with 25th to 75th and 10th to 90th percentile bands.

Solar Energy

This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.

The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.9 months, from April 25 to August 21, with an average daily incident shortwave energy per square meter above 7.5 kWh. The brightest day of the year is June 18, with an average of 8.6 kWh.

The darker period of the year lasts for 3.2 months, from November 6 to February 12, with an average daily incident shortwave energy per square meter below 4.1 kWh. The darkest day of the year is December 26, with an average of 2.9 kWh.

The average daily shortwave solar energy reaching the ground per square meter (orange line), with 25th to 75th and 10th to 90th percentile bands.

Topography

For the purposes of this report, the geographical coordinates of San Fernando are 34.282 deg latitude, -118.439 deg longitude, and 1,086 ft elevation.

The topography within 2 miles of San Fernando contains significant variations in elevation, with a maximum elevation change of 522 feet and an average elevation above sea level of 1,079 feet. Within 10 miles contains significant variations in elevation (4,295 feet). Within 50 miles also contains extreme variations in elevation (10,062 feet).

The area within 2 miles of San Fernando is covered by artificial surfaces (69%) and shrubs (31%), within 10 miles by shrubs (52%) and artificial surfaces (44%), and within 50 miles by shrubs (43%) and artificial surfaces (20%).

Data Sources

This report illustrates the typical weather in San Fernando, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.

Temperature and Dew Point

There are 4 weather stations near enough to contribute to our estimation of the temperature and dew point in San Fernando.

The estimated value at San Fernando is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between San Fernando and a given station.

Other Data

All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.

Disclaimer

The information on this site is provided as is, without any assurances as to its accuracy or suitability for any purpose. Weather data is prone to errors, outages, and other defects. We assume no responsibility for any decisions made on the basis of the content presented on this site.

We draw particular cautious attention to our reliance on the MERRA-2 model-based reconstructions for a number of important data series. While having the tremendous advantages of temporal and spatial completeness, these reconstructions: (1) are based on computer models that may have model-based errors, (2) are coarsely sampled on a 50 km grid and are therefore unable to reconstruct the local variations of many microclimates, and (3) have particular difficulty with the weather in some coastal areas, especially small islands.

We further caution that our travel scores are only as good as the data that underpin them, that weather conditions at any given location and time are unpredictable and variable, and that the definition of the scores reflects a particular set of preferences that may not agree with those of any particular reader.